The present invention generally relates to head worn devices and methods for mitigating or preventing motion sickness. Motion sickness can include vertigo, simulation sickness, gaming sickness, spatial disorientation, dizziness, vision induced motion sickness or vection induced motion sickness in 2-D, 3-D, or 4-D environments, including the viewing of displays such as with operation of remote devices, in simulators, medical imaging, surgical training or operations, virtual environments, scientific visualization, space use, or gaming. The head worn devices can be attachable and detachable from another device attached to the head, such as a helmet or glasses; the head worn devices can be integrated into another device attached to the head, such as a helmet or glasses; or the head word devices can be standalone devices attached to the user's head. Mitigation and prevention of motion sickness more specifically relates to the use of a visual reference to prevent conflicting sensory mismatch between the visual, proprioceptive, and inner ear senses. The visual reference may be controlled through a mechanical or fluid system responsive to gravitational forces. The prevention and control of motion-related sickness and spatial disorientation can minimize symptoms of nausea, vomiting, and factors that compromise human performance in motion-related environments.
Motion Sickness occurs because of the mismatched sensation with what is seen compared to what is felt and what is perceived in the inner ear. There are many different types of provocative motion environments that can induce motion sickness, motion-induced vision sickness, and other variants of spatial disorientation and vertigo. Often these provocative environments are intensely stimulating but for many people with motion intolerance, the provocative motion environment may be subtle. Provocative motion environments can be associated with locomotion such as ships, hovercraft, aircraft, automobiles, and trains. The complex accelerations generated by fairground amusements, such as swings, roundabouts (merry-go-rounds), roller coasters and so on, can be highly provocative. Astronauts/cosmonauts can suffer from motion sickness (space-motion sickness) when they first make head movements in the abnormal force environment (weightlessness) of orbital flight. Provocative motion environments can also be experienced by moving visual stimuli, without any physical motion of the observer. Typical examples of visually stimulating environments include participating in virtual reality platforms or systems. Virtual reality (VR), Augmented Reality (AR), Multi-Dimensional (MD) and Synthetic environmental systems encompasses a set of technologies that place the user in a computer-generated, three-dimensional environment and all can encompass a provocative motion environment for the user. Augmented reality mixes the physical with the virtual, layering computer-generated objects and information onto the real world. These types of environments can create a VR experience that truly fools the brain. The feeling of experiencing reality while in a VR, AR, MD and synthetic systems is a very profound one, as the brain interprets sensory data as though actually experiencing an event. For many using these platform systems, the result is visually induced motion sickness. Simulator sickness is another example of motion sickness, and simulator sickness in virtual reality environments (VRE) has become an important issue. Most provocative motion environments cause three distinct, but possibly related, responses: reflexive eye movements (EM), sensory conflict (SC), and postural instability (PS). A provocative motion stimulating environment can be defined as being immersed in an environment where the user can experience vestibular stimulation, (such as with vehicular motion), visual stimulation (such as with simulator, VR, AR, MD, or other synthetic visual systems), postural or proprioceptive disturbances (such as with experiencing vertical vibrations with frequencies between 0.16-2.0 Hz) and even with sequentially based low frequency auditory signals. Some examples of provocative motion environments include vehicle use, an AR (augmented reality environment), a multi-dimensional environment, a synthetic or computer generated synthetic environment, and/or a visual induced environment, such as watching motion while the user is motionless.
Mismatched sensation of what is seen compared to what is felt and what is perceived in the inner ear can occur any time when the brain perceives that the body is in motion (through signals originating in the labyrinth and transmitted to the brain by the vestibular nerve), but the motion sensed does not match what the eye can see and verify. For example, a passenger traveling along a winding road in a vehicle experiences linear and angular accelerations as the vehicle travels around a curve. The response of the vestibular sensing system to the acceleration caused by the motion of the vehicle will not match the visual perception unless the person is constantly viewing the road so that the perception of the person's inner ear matches that which is visually perceived. Passengers in a vehicle who are doing other tasks such as reading will have a visual perception that does not match the senses of their inner ear and may experience symptoms of motion sickness. Additionally the sensory mismatch can occur when the eye perceives motion, but the labyrinth does not provide confirming signals to the brain (such as watching a rocking boat while motionless). It can affect anyone and depending on the degree of provocation can be quite disabling. Balance receptors respond to gravity, velocity and changes in velocity. Some of the inner ear receptors sense linear or tilt motion and other sense rotational movement.
Motion Sickness, spatial disorientation and vertigo have been acknowledged as a widespread problem, affecting a significant portion of world population to varying degrees. Researchers report that up to 60% of the population has some motion intolerance. It has been reported that motion sickness affects nearly one third of all people who travel by land, sea, or air. Individuals are affected daily by motion sickness and spatial disorientation while riding in automobiles, trains, buses, planes or other transport. The Greeks provided the first written historical account of motion sickness. The Roman Cicero claimed he would rather be killed in battle than suffer the tortures of nausea maxis. Motion sickness has even been used as a form of punishment. One of the world's most famous mariners, Admiral Lord Nelson reportedly never adapted to motion sickness. Napoleon's General Carbuccia refused to use camels for Napoleon's army, because of the issues with motion (2) Even Lawrence of Arabia is reported to have experienced Camel sickness.
It is also known that some people are more susceptible than others; for example, women are more sensitive to motion than men by a ratio of about 5:3. Some are more susceptible due to physical reasons such as age. Studies show a significant genetic contribution to a propensity to motion sickness. It has been well observed that poor ventilation, bad odors, smoking, eating large fatty meals and alcohol can make motion sickness more pronounced. Susceptibility to motion sickness begins at about age two, and for most will peak in adolescence and decline gradually. However, many adults remain highly sensitive caused by any motion, particularly when combined with either an absence of a visual reference or to significant levels of visual stimuli. In fact, a provocative visual stimulus has been shown to be the most influential cause of motion sickness symptoms. Reading in a moving vehicle, abruptly moving the head (such as looking down) while a vehicle is moving can provoke symptoms. Fear, anxiety and other psychological factors can contribute to the onset of motion sickness. Some people can get sick just thinking about an upcoming trip or flight.
For those who experience the symptoms, the result is often disabling, with nausea, vomiting, sweating, and unsteadiness, while feeling cold, clammy and disorientated. In addition, the term “sopite syndrome” was coined to refer to the apathy, passivity, and lack of concentration characteristic of motion sickness.
Of the 12.6 million passengers who cruise annually, an estimated 20% or more become seasick. The occurrence of motion sickness can approach 100% in cruise ship passengers on rough seas. Seasickness, a common form of motion sickness, is also frequent among naval personnel, where 60% to 90% percent of inexperienced sailors can suffer from seasickness. Experienced crewmembers are not immune. Up to 60% of experienced crewmembers have been affected in these conditions. This becomes a major problem in modern seamanship in which small crews are responsible for the operation of sensitive and sophisticated equipment. During the invasion of Normandy, in World War II, the seas were reportedly very high causing the landing crafts to pitch and yaw, like a kite in a windstorm. The soldiers were lying and sitting in flat bottomed crafts and were using huge buckets for vomiting and urinating, which soon overflowed after boarding. As thousands of men were lying in the vomit, urine and rain they debarked in a state of terror, which was compounded by their symptoms of seasickness, and attempted to perform at a high level in order to survive in combat. Many of these soldiers had to overcome the most debilitating effects of motion sickness to survive. There are additional volumes of data that document the severe effect of motion sickness on human performance of even basic tasks.
Spatial disorientation and motion sickness are significant problems in aviation. In motion provocative environments, spatial disorientation and motion sickness cause not only a loss in human performance (affecting cognitive and motor skills), but also a loss of expensive aircraft and human life. Thousands of deaths have been attributed to aviation accidents caused by being spatially disoriented. In a review of aviation mishaps from 1987-1997 by the Aviation Safety Foundation of the Aircraft Owners and Pilots Association, there was an average of one fatal SD accident every 11 days in the United States. These accidents have resulted in a fatality rate of 91% in the General Aviation (GA) community and a 69% fatality rate in the U.S. Military. There are over 650,000 civilian pilots in the United States alone. Non-instrument rated pilots who fly into the clouds historically have 178 seconds before ground impact. The death of John F. Kennedy Jr. was an example of a spatial disorientation accident and unknown to many were thirty other reported crashes that same day, with at least one other due to spatial disorientation. According to FAA statistics, SD and loss of situational awareness causes 15%-17% of fatal general aviation crashes annually. More significantly, 9 out 10 SD mishaps result in a fatality. From 1980-2000, the USAF experienced 1,087 aviation fatalities with over 14% (172) directly attributed to SD at a cost of over $1.54B. A recent study has shown that almost 90-100% of aircrews have reported at least one incidence of spatial disorientation (SD) during their flying careers. SD accounted for 11-14% of USAF mishaps and a mishap fatality rate of 69%, with risk of SD significantly increased in helicopters and fighter/attack aircraft and at night. The most frequent experienced SD episodes are “leans” (92%), loss of horizon due to atmospheric conditions (82%), misleading altitude cues (79%), sloping horizon (75%), and SD arising from distraction (66%). The Air Force Safety Center FY 93-02 mishap analysis reported that Class A mishaps resulted in 243 destroyed aircraft, 310 fatalities, and an economic loss of $6.23 billion. Airsickness has also been identified as a flight training issue. A motion sickness history questionnaire obtained from student pilots in the Air Force revealed an incidence of airsickness of 50%. In a questionnaire to B-1 and B-52 bomber crewmembers, it was reported to be a frequent occurrence among non-pilots in both aircraft, and experienced crewmembers were more likely to report an impact on their duties.
Space motion sickness is experienced by 60%-80% of astronauts during the first 2-3 days in micro gravity and by a similar proportion during their first few days after return to Earth. Up to 90% of astronauts experienced spatial disorientation during reentry and landing of the shuttle, with prevalence proportional to the length of the mission. Exposure to micro gravity rearranges the relationships among signals from visual, skin, joint, muscle, and vestibular receptors. Congruence between vestibular signals and those from other receptors, as well as between the vestibular otolith and semicircular canal receptors, is disrupted by the absence of gravity. This lack of congruence between sensory exposure to provocative real or apparent motion leads to the progressive cardinal symptoms of terrestrial motion sickness. Space motion sickness may vary slightly with flushing more common than pallor, stomach awareness, malaise, loss of appetite, and sudden vomiting, often without prodromal nausea. The only remedy to space motion sickness at this moment is drug therapy while stationed in space, a decidedly non-optimal solution. Additionally during training for space flight students aboard the zero-G flight simulator routinely experience motion sickness. When people go up into space, many will immediately get space sickness, according to NASA's Biomedical Research and Countermeasures Program. While a few astronauts are apparently immune, most can experience symptoms ranging from mild headaches to vertigo and nausea. In extreme cases prolonged vomiting can make an astronaut dehydrated and malnourished. Motion sickness remains a persistent problem in space flight. Proposed etiological factors in the elicitation of space motion sickness include fluid shifts, head movements, visual orientation illusions, Coriolis cross-coupling stimulation, and otolith asymmetries. Space sickness relieves itself after about 3 days, for some although individual astronauts and cosmonauts may have a relapse at any time during their mission and continue to take medication, which can alter their cognitive and motor function. For those personnel in sub-orbital flights performing a research job or experiment for a client, they cannot afford to be sick or disoriented or distracted. They have four to five minutes on a sub-orbital flight to get a job done. If afflicted with space sickness human performance is compromised. In the private space tourism companies it is a known fact that passengers are very likely to have space sickness, or its more scientific name, Space Adaptation Syndrome (SAS). Even with medication, most astronauts experience it when they go to space to varying degrees, from mild nausea or a headache to vomiting. SAS is a main reason that extra-vehicular activities (EVA) outside of the space shuttle are done only after a few days in space, as vomiting inside a space suit is lethal. Some astronauts who show an exceptional tolerance to motion sickness when flying jets suffer the worst symptoms upon arriving in space. Astronauts returning from extend space flights routinely have to learn to reorient themselves in the terrestrial environment. Motor and cognitive skills are often observed to be severely degraded during the re-acclimation period. This is due to the sudden reintroduction of gravitational cues and stimulus of proprioceptors. The time needed to re-acclimate to the terrestrial environment is about three days per week in space.
Vestibular disorders affect an estimated 20% of the general population. 90 million Americans (42% of the population) will complain of dizziness at least once during their lifetimes, and 80% of these complaints will have a vestibular component. There are more than 10 million physician visits annually for dizziness or balance complaints (Source: National Balance Centers/Vestibular Disorders Association), with a cost of greater than one billion dollars per year. Postural control requires a complex interaction of visual and proprioceptive sensory inputs providing external orientation reference frames while the internal reference frame is provided by the vestibular system. Persistent vestibular dysfunction can occur following a variety of insults to the vestibular system, including infections, ototoxicity, trauma, chronic ear pathology, tumors, Meniere's disease, surgery and other idiopathic causes. Acoustic tumor surgery and vestibular nerve section, performed for disabling vertigo in patients with Meniere's disease, usually result in rapid compensation. However some patients, particularly non-Meniere's disease patients, have a prolonged period of unsteadiness without compensation for a long period of time. The resulting disability can be devastating. It has also been shown that postural instability precedes motion sickness with provocative visual stimuli. All these vestibular impairments cause disequilibrium, blurred vision, disorientation, and vertigo, which in turn cause dysfunction in many activities of daily living and in social interactions that traditional medical treatments may not address.
Medical rehabilitation, overcoming chronic illness, recovery from surgery, and recovery from trauma represent additional applications. Presently, 10 million patients receive balance (vertigo) medical rehabilitation therapy costing $1 billion annually. Reasons for treatment are due to disease affecting the vestibular organs, rehabilitation from surgery on the balance organs, recovery from trauma to the head and rehabilitation in patients learning to use prosthetics in the lower extremities. Clinical tests conducted by the inventor funded by the National Institutes of Health (NIH) resulted in 96% effectiveness in resolving balance issues associated with these various maladies. Regarding overcoming chronic illness, many patients with the NIH test group with chronic balance disorders were able to return to functionality after enduring years of other ineffective treatments. The visual display reduced the average number of clinical visits from 25 rehabilitation treatments to 5 and in several cases proved to be the only effective treatment the patient had ever experienced. Regarding recovery from surgery, within the NIGH test group, the visual display proved to reduce the average number of clinical visits from 25 rehabilitation treatments to 5 and in several cases proved to be the only treatment effective. Regarding recovery from trauma, head trauma and injury to the inner ear often result in temporary balance problems. The loss of proprioception with injuries to extremities can also result in loss of balance. In tests the visual display greatly shortened rehabilitation and recovery times and in some cases was the only treatment effective to aid recovery due to head trauma, vestibular injury and limb injury. Regarding rehabilitation using prosthetics to lower extremities, physicians associated with the US Army Center for the Intrepid, based at Brook Army Medical Center in San Antonio Tex. report that many soldiers who have suffered injury to the lower extremities or amputation have balance issue while learning to use prosthetics. This is due in part to loss of proprioception inputs associated with the loss of the limbs and new weight distribution associated with the prosthetics. It is hypothesized our technology will greatly shorten rehabilitation time by providing strong visual cues to offset the loss of sense of touch due to limb loss and aid balance while learning to use the new limbs.
Simulation sickness, or simulator sickness, is a condition where a person exhibits symptoms similar to motion sickness caused by playing computer/simulation/video games. Simulation sickness or gaming sickness cause symptoms quite similar to that of motion sickness, and can range from headache, drowsiness, nausea, dizziness, vomiting and sweating. Research done at the University of Minnesota had students play Halo for less than an hour, and found that up to 50 percent felt sick afterwards. In a study conducted by U.S. Army Research Institute for the Behavioral and Social Sciences in a report published May 1995 titled “Technical Report 1027—Simulator Sickness in Virtual Environments”, out of 742 pilot exposures from 11 military flight simulators, “approximately half of the pilots (334) reported post-effects of some kind: 250 (34%) reported that symptoms dissipated in less than 1 hour, 44 (6%) reported that symptoms lasted longer than 4 hours, and 28 (4%) reported that symptoms lasted longer than 6 hours. There were also 4 (1%) reported cases of spontaneously occurring flashbacks.” Simulator sickness is another example of motion sickness, and many military pilots have reported at least one symptom following simulator exposure. In a study of Coast Guard aviators undergoing flight simulator testing, 64% reported adverse symptoms during the first simulator flight and 39% did so during the last flight. 36% of pilots reported motion sickness when training on a Blackhawk flight simulator.
More recently, simulator sickness in virtual environments (VE) has become an important issue. Virtual reality is already a popular technology for entertainment purposes, and both the U.S. Army and Navy are interested in the training applications of virtual environments. However, some users of VE experience discomfort during, and sometimes after, a session in a simulated environment, in equivalent fashion to simulator sickness already noted for flight and driving simulators. Similarly, in casual gaming, a number of modern electronic games feature a virtual control interface. These displays are often not see-through and present highly motion provocative visual displays.
Motion sickness due to virtual reality is very similar to simulation sickness and motion sickness due to films. In virtual reality, however, the effect is made more acute as all external reference points are blocked from vision, the simulated images are three-dimensional and in some cases stereo sound that may also give a sense of motion. The world's most advanced simulator, the NADS-1, located at the National Advanced Driving Simulator, is capable of accurately stimulating the vestibular system with a 360-degree horizontal field of view and 13 degree of freedom motion base. Prior studies have shown that exposure to rotational motions in a virtual environment can cause significant increases in nausea and other symptoms of motion sickness. Counter Vertigo in Virtual Pilot Vehicle Interface. Operators of unmanned aerial systems (UAS) routinely experience spatial disorientation due to limited visual cues in sensor control displays. Further, experiments using a virtual pilot vehicle control interface, where the pilot controlled the UAS based on visual cues derived directly through sensors (placing the point of view on the nose of the aircraft) versus via CRT control displays led to cases of SD and motion sickness. It is believed our technology will prevent SD/MS in both UAS PVI environments.
Vision Induced Motion Sickness, such as the motion sickness due to films and other video is a type of sickness, is particularly prevalent when susceptible people are watching films on large screens such as IMAX but may also occur in regular format theaters or even when watching TV. For the sake of novelty, IMAX and other panoramic type theaters often show dramatic motions such as flying over a landscape or riding a roller coaster. There is little way to prevent this type of motion sickness except to close one's eyes during such scenes or to avoid such movies. In these cases, motion is detected by the visual system and hence the motion is seen, but no motion or little motion is sensed by the vestibular system. Motion sickness arising from such situations has been referred to as Visually Induced Motion Sickness (VIMS). Movie-induced motion sickness has become more prevalent due to new cinematographic techniques. For example, there are claims that “The Hobbit: An Unexpected Journey” has caused motion sickness and nausea among viewers. The film having been shot using 3-D and new 48 fps (frames per second) technology, double the standard rate of 24 fps that has been used to shoot films since 1927. Additionally, in regular format theaters, another example of a movie that caused motion sickness in many people was The Blair Witch Project. Theaters warned patrons of its possible nauseating effects, cautioning pregnant women in particular. Blair Witch was filmed with a handheld camcorder, which was subjected to considerably more motion than the average movie camera. Home movies, often filmed with a hand-held camera, also tend to cause motion sickness in those that view them. The cameraperson rarely notices this during filming since his/her sense of motion matches the motion seen through the camera viewfinder. Those who view the film afterward only see the movement, which may be considerable, without any sense of movement. Using the zoom function seems to contribute to motion sickness as well as zooming is not a normal function of the eye. The use of a tripod or a camcorder with image stabilization technology while filming can minimize this effect. 55% of people who watch 3D movies have MS. Following the market expansion of movies filmed with three-dimensional (e.g. 3D) technology and televisions equipped with 3D displays for the home entertainment, there has been an increasing concern about possible side effects on spectators. It has been suggested that the viewing of 3D stereoscopic stimuli can cause vision disorders to manifest in previously asymptomatic individuals. The prevalence of health outcomes on 3D movie spectators appears to be increasing in domestic environments.
Research on professional exposures to virtual reality systems, vehicle simulators, and stereoscopic displays have reported that several adverse health effects can be induced by viewing motion images, including visual fatigue (also termed asthenopia), or eyestrain, vection induced motion sickness and visually induced motion sickness (VIMS). Symptoms of visual fatigue induced by images comprise eye discomfort and tiredness, pain and sore around the eyes, dry or watery eyes, headaches and visual distortions such as blurred and double visions, and difficult in focusing. The main physiological mechanism involved with the onset of visual fatigue concerns the intense eye accommodation activity of 3D movie viewers, such as focusing and converging. It has been argued that eye focus cues (accommodation and blur in the retinal image) target the depth of the display (or of the movie screen) instead of the displayed scene, generating unnatural depth perception. Additionally, uncoupling between vergence and accommodation affects the binocular fusion of the image. Both processes may generate visual fatigue in susceptible individuals. In addition to symptoms of visual fatigue, viewers of 3D may experience nausea (nausea, increased salivation, sweating) and disorientation (dizziness, vertigo, fullness of head). Those symptoms are indicative of VIMS, a condition that may onset during or after viewing dynamic images while being physically still, when images induces in the stationary spectator a sense of vection (i.e. illusion of self-movement). The most accepted explanation for VIMS is the classical conflict theory based on the mismatch between the visual, the proprioceptive and the vestibular stimuli. In this case, the visual system feels vection while the vestibular and proprioceptive systems do not transmit signals consistent with motion. Notably, although VIMS and visual fatigue are different conditions, they probably share some common biological mechanisms.
The specific disturbance deriving from viewing 3D movies has been named “3D vision syndrome” but the relative occurrence of different symptoms in spectators and the individual characteristics that make some individuals more susceptible than others still remain to be described. Previous research showed that occurrence of self-reported symptoms in young healthy adults during or immediately after watching a 3D movie may be high, although often quickly disappearing once they finished viewing. Factors reported to be associated with VIMS can be categorized into (i) factors associated with the visual stimuli provided to viewers, (ii) factors associated with the position from where the viewers are watching the movie and (iii) the psychophysiological conditions of the viewers. Examples reported in literature include (but are not limited to): the characteristics of the (moving) images (e.g. the optic flow) such as the earth axis along which the visual field is made rotating, the amplitude of the field of view, the display angle, the feeling of immersion or presence, the co-presence of vection, the display types, postural instability, habituation, age, gender, and anxiety levels of viewers. Interactions and additive effects among factors may also be present, making difficult to predict the final outcome (if a given individual will or will not suffer VIMS).
Earlier experiences of visual discomfort observed in 3D display viewers led to the hypothesis that the conflict between vergence and accommodation stimuli is the cause of such visual discomfort. Controlled experimental conditions in which the effect of the vergence-focal conflict on visual fatigue could be isolated from other variables confirmed such explanation. Additionally, it has been argued that 2D movie viewers tend to focus at the actors while the eye movement patterns of 3D viewers are more widely distributed to other targets such as complex stereoscopic structures and objects nearer than the actors. This behavior might increase the vergence-accommodation mismatch, increasing the visual stress on 3D spectators. The higher intensity of visual symptoms when participants were exposed to the 3D movie compared to the 2D movie observed in our study could be taken as a large-scale evidence of such hypothesis. Possibly, a partially different mechanism is involved in the onset of nausea and disorientation related symptoms. Nausea, dizziness and vertigo are connected to vestibular disturbance and the visual—vestibular interactions and the classical sensory conflict theory can explain the onset of symptoms in susceptible individuals. The public health relevance of VIMS was raised some years ago in Japan when 36 (out of 294) high school students were hospitalized for motion sickness after watching a movie characterized by unexpected whole image motion and vibration (the so called Matsue movie sickness incident). A previous multivariate analysis suggested that seeing a 3D movie increases the simulator sickness questionnaire (SSQ) scores. Besides the exposure to 3D, significant predictors of higher SSQ total score were car sickness and headache after adjusting for gender, age, self-reported anxiety level, attention to the movie and show time. The use of glasses or contact lenses does not seem to increase the risk of raising SSQ scores. Women with a history of frequent headache, carsickness (and possibly dizziness, which is correlated with the above mentioned variables) may be more susceptible to VIMS than others. The relationships between motion sickness, vertigo, dizziness, and migraine is well documented and 3D movies may interact with these conditions to produce more symptoms than 2D movies.
Clearly viewing 3D movies can increase rating of nausea, oculomotor and disorientation. Analogous to riding a roller coaster, for most individuals the increases in symptoms is part of the 3D experience and enjoyment and these experiences is not necessarily an adverse health consequence. However, some viewers will have responses that in other contexts might be unpleasant. In particular, women with susceptible visual-vestibular system may have more symptoms when watching 3D movies. Individual variability of the 3D exposure including the length of the movie, the angle of view and the pre exposure baseline conditions are potential predictors of visual discomfort that may warrant future investigation. As noted by others, 3D viewing may increase task burdens for the visual system, and susceptible individuals may develop a “3D vision syndrome”. Due to increasing commercial releases of 3D movies and displays for home and professional use it is likely that more people will complain about these symptoms.
The worldwide increasing popularity of commercial movies showing stereoscopic (e.g. three dimensional—3D motion images is documented by the fact that 3D releases are generating more revenues than the same movie released in 2D. In parallel with the expansion of digital 3D cinema systems, several consumer-electronics manufacturers released 3D televisions and displays for the home entertainment. For example, more than 300 3D videogames are already available for computers and consoles. Stereoscopic displays are becoming also very important for no leisure applications such as vision research, operation of remote devices, medical imaging, surgical training, scientific visualization, virtual prototyping, and many others. In the near future, it is predictable that more and more people will pass increased portion of time (either leisure or work time) viewing 3D motion images, raising concern about the 3D image safety and possible adverse side effects on end users.
There are concerns about possible adverse effects of watching novel visual images and experience of VR, such as photosensitive seizures, visually induced motion sickness (VIMS) and eyestrain. In particular, when a patient watches an image changed based on real-time information of his head-position, which is sometimes used in VR system, there is a possibility that he watches unexpected images, such as upside-down or rotating, and then he feels VIMS. Since almost all users of the rehabilitation system are aged and/or physically weak, mental or physical stress on them caused by VIMS is typically greater than on healthy users.
Stereoscopic three-dimensional (3D) displays and the viewing content are designed to heighten a sense of immersion and presence for viewers. As manufacturers increasingly offer 3D TV models and 3D TV programming content and commercial movies are made available to viewers at home, there is an increasing concern about visual, ocular, and physical discomfort reported by some 3D viewers. The commonly held explanation of visual symptoms in 3D viewing is that it stimulates a different vergence and accommodative demand than encountered in real 3D. The 3D displays provide stereoscopic visual stimulation by projecting separate images to each eye. Each image is a view of the scene from a slightly different angle, thereby simulating the different views of the eyes in a real scene. Stereoscopic depth provides relative depth information; i.e. it informs the viewer about the relative (not absolute) distances of objects with respect to one another. 4D/5D Theatre Technology: In recent years, 3D viewing has been accompanied with synchronization of some special effects installed in the theatres. When it rains in the movie, the audience also experiences the same. When there's lightening in the movie, the same happens in the theatre. Other effects include wind, fog, smell, sensation etc. These are called 4D effects. Theatres with 3D viewing, 4D effects and some seat movements are called 4D theatres. In cases of 5D theatres, seats move in synchronization with motion in the movie thus providing immersive experience to the audiences. For this at least six—directional seat movements are required: left and right rolls; forward and backward tilts; and up and down movements. These theatres show an excellent integration of 3D technology, audio, motion synchronization and multiple special effects using specialized software. For synchronization, using special software, movies and seat motion is pre-programmed.
Rotating devices such as centrifuges used in astronaut training and amusement park rides such as the Rotor, Mission: Space and the Gravitron can cause motion sickness in many people. While the interior of the centrifuge does not appear to move, one will experience a sense of movement. In addition, centrifugal force can cause the vestibular system to give one the sense that downward is in the direction away from the center of the centrifuge rather than the true downward direction. When one spins and stops suddenly, fluid in the inner ear continues to rotate causing a sense of continued spinning while one's visual system no longer detects motion.
There have been many theories about the cause of motion sickness, spatial disorientation and vertigo. Currently, the sensory conflict theory appears to be the dominant theory favored by researchers in that the majority of investigators agree that it is not solely the movement or movement stimulus that results in motion sickness, but rather a conflict in movement information detected by the different sensory modalities of the inner ear, vision, and proprioception. A conflict of visual and vestibular (inner ear) information, as it relates to postural control and visual stabilization, is certainly a critical factor. Investigators now also agree that it is primarily an incongruence of visual and vestibular sensory information regarding movement and orientation that results in motion sickness. Incongruence between the semicircular canals and the otolithic organ input has also been implicated as the provocative stimulus in seasickness and in the onset of motion sickness associated with weightlessness. Another contributing factor which may trigger susceptibility to motion sickness may be the mass size differences of the utricular otoconia between the left and right sides in some people, as seen in fish.
Within the sensory conflict concept has arisen an “incongruence in the visual system” theory, which can be called a Velocity Storage Theory. The vestibular nerve communicates head velocity and estimates of angular displacements require further central nervous system processing (i.e. integration). There is some inconsistency between velocity-based ocular studies and displacement-based perceptual studies. Most oculographic studies of vestibular function are based on measurements of the slow phase velocity of the eye. If a monkey or man is rotated at constant velocity in the dark, the velocity of the slow phase of the nystagmus decays exponentially with a time constant of Fifteen to Twenty seconds (15-20 sec). Direct recordings of the vestibular nerve in monkeys have shown the head velocity signal, transmitted by the vestibular nerve, has a time constant of decay of only Seven to Ten (7-10 sec). The duration of the eye velocity curve (i.e. a nystagmus response) is therefore longer, outlasting the sensation or perception curve. The perception of angular velocity is based on signals subserved by the brainstem velocity storage system. Thus the head velocity signal appears to be stored in the brain and then released onto ocular motor neurons for the generation of nystagmus. Brainstem circuits in the vicinity of the vestibular nuclei, behaving as mathematical integrators, are thought to mediate this storage process. There is evidence that motion sickness is generated through this velocity storage and can be reduced by reducing the angular vestibular ocular reflex time constant. Others support a multi-factor explanation of motion sickness, involving both sensory conflict and eye movement.
Ordinarily, eye movements prevent slip of images upon the retina from exceeding about 4 degrees per second. If retinal image velocity (RIV), commonly called, “retinal slip,” exceeds 4 degrees per second, then visual acuity begins to decline and oscillopsia (an illusory movement of the stationary world) may result. Pursuit eye movements allow primates to follow moving objects with the eyes. When a target of interest starts to move, after a latency period of 120 ms, the eye accelerates smoothly in the direction of target motion to reduce the error between eye velocity and target velocity, i.e., retinal slip. Eye acceleration increases with the retinal slip and saturates at a value between 200 and 400°/s2 for non-periodic tracking in primates. In the middle of this acceleration period, a “catch-up” saccade is generated to reduce the error between eye and target positions that accumulated during the latency period. The catch-up saccade brings the image of the target on the region of the retina where visual acuity is the highest, the fovea. In primates, smooth pursuit gain, the ratio of eye velocity to target velocity, is close to unity. This indicates that at the end of the acceleration period, eye velocity almost perfectly matches target velocity. The period during which eye velocity matches target velocity is often referred to as steady-state pursuit. During steady-state pursuit in primates, eye velocity oscillates around a mean value. The frequency of this oscillation varies between 3.8 and 6 Hz and could reflect the delays inherent in the operation of a visual feedback loop. Retinal image slip promoted by fixational eye movements prevents image fading in central vision. However, in the periphery a higher amount of movement is necessary to prevent this fading. Even when the eye is fixating a point target it is not totally motionless because fixational eye movements keep it moving incessantly. There are three types of fixational eye movements: tremor, drift, and microsaccades. Tremor is an aperiodic, wave-like motion with velocities of approximately 20 minutes of arc/sec and amplitude smaller than the diameter of a foveal cone. Drift movements occur simultaneously with tremor and are larger and slower than tremor, with velocities in the order of 4 minutes of arc/sec and mean amplitudes of around 2-5 minutes of arc. This amplitude corresponds to a movement of the retinal image across a dozen photoreceptors. Fixational microsaccades, also called ‘flicks’ in early studies, are small and fast eye movements that occur during voluntary fixation. Typically with peak velocities above 600 minutes of arc/sec, their amplitude ranges from 1 to 120 minutes of arc and they carry the retinal image across a width corresponding to several dozen to several hundred photoreceptors.
Despite this incessant retinal motion, images are perceived as static and clear. The visual system has mechanisms to deal with movement and the eventual blur resultant from the retinal image slip caused by fixational eye movements. These mechanisms fail when the amount of movement is above their capacity of neutralization. In these conditions, the image is perceived as blurred due to motion smear. An immediate consequence of blur is a diminution of resolution. Gaze control in various conditions is important, since retinal slip deteriorates the perception of 3-D shape of visual stimuli. Several studies have shown that visual perception of 3-D shape is better for actively moving observers than for passive observers watching a moving object. When a stationary viewer is watching compelling moving scene, he or she can report sensation of self-motion illusion (called vection). Vection has been found to be correlated with levels of visual induced motion sickness (VIMS) and postural status. The correlation between vection and VIMS is consistent with the sensory conflict theory because sickness is generated in a sensory conflict situation where a person is reporting illusion of self-motion while remain physically stationary. The correlation between vection and VIMS has led to the term “vection induced motion sickness”. One theory linking VIMS with inappropriate eye movements is consistent with the findings that suppression of eye movements by fixation can significantly reduce levels of VIMS. It has been hypothesized that the afferent signals in the ocular muscles will trigger vagal nuclei, resulting in a range of sickness symptoms associated with the autonomous nervous systems—the nystagmus theory. Because eye movements follow foveal stimulation and vection follows peripheral stimulation, the nystagmus theory indicates that in the presence of foveal stimulation, sickness will correlate with eye movements but not necessarily with vection. Since then, there have been competing studies reporting the decoupling between vection and VIMS as well as coupling between vection and VIMS. Some have felt that vection and motion sickness can be distinct phenomena and have further described Optokinetic stimulation generating circular-vection, and vection generated during a simulation of forward motion in a car as linear vection. In a prior study using an Optokinetic drum with this technology it was seen that both vection scores and simulator sickness scores were statistically significantly lower than when the technology was not used.
Eye fixation has consistently been shown to significantly reduce levels of visually induced motion sickness (VIMS). The common belief is that the reduction in VIMS is associated with the suppression of eye movement. One study proposed an alternative theory to associate the reduction of VIMS due to eye fixation with the increases in peripheral retinal slip velocity. Results showed that when participants were watching striped patterns rotating at 7 dps (degrees per second), eye fixation significantly increased the peripheral retinal slip velocity from about 2.6 dps to 7 dps and but failed to cause a significant change in the average rated levels of VIMS. However, in the same study, increasing the peripheral retinal slip velocity of moving patterns from 2.6 dps to 35 dps in the presence of OKN significantly increased the rated levels of nausea from 2.1 (mild unpleasant symptom) to 3.6 (mild to moderate nausea). It might be that when watching patterns moving at 7 dps, eye fixation introduced two competing effects: (i) suppression of eye movement reduced levels of VIMS and (ii) increases in peripheral retinal slip velocity increased levels of VIMS. However introducing fixation into stimulated or a VE environment reduces the foveal slip and motion sickness. Retinal image slip promoted by fixational eye movements prevents image fading in central vision. However, in the periphery a higher amount of movement is necessary to prevent this fading. The effects of increased retinal image slip are different for simple (non-crowded) and more complex (crowded) visual tasks. Prior results provide further evidence for the importance of fixation stability on complex visual tasks when using the peripheral retina. This technology can prevent both foveal slip and peripheral retinal slip velocity in a provocative motion environment.
Mismatches can be caused where there are differences in stimuli as processed by the brain. Mismatches can occur where there is motion, or where there is no motion. These mismatches may be caused by delays in the delivery or processing of the stimuli or mismatch of stimuli even without delay. Examples of mismatches are seen in persons suffering from vertigo or persons in a virtual space such as a video game or flight simulator or targeting system. A solution is needed that will enable a person to participate in activities where visual scene motion does not evoke illusory self-motion or motion sickness and participate in motion provocative activities without having motion sickness, spatial disorientation, vertigo and loss of human performance activities.
There is a need for improvements to systems and methods that avoid vertigo, motion sickness, and spatial disorientation integrated in motion sensory provocative environments to avoid problems associated with compromised human performance or even loss of user control. Such an improvement can have application in mitigating, preventing or controlling symptoms of motion sickness, simulation sickness, gaming sickness, spatial disorientation, dizziness, 3-D vision syndrome or vision induced motion sickness in the environments of 3-D or 4-D motion viewing, or viewing any stereoscopic displays such as with operation of remote devices, in simulators, medical imaging, surgical training or operations, virtual environments, scientific visualization, space use, or with gaming devices. An ideal device would be as simple and low cost as possible to broaden its market appeal. It should be able to operate in any kind of lighting environment ranging from broad daylight to nighttime conditions. Ideally, the device would not require any power source.
It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood that the invention is not necessarily limited to the particular embodiments illustrated herein.